Positive-Working Photoimageable Bottom Antireflective Coating

ABSTRACT

The present invention relates to a positive bottom photoimageable antireflective coating composition which is capable of being developed in an aqueous alkaline developer, wherein the antireflective coating composition comprises a polymer comprising at least one recurring unit with a chromophore group and one recurring unit with a hydroxyl and/or a carboxyl group, a vinyl ether terminated crosslinking agent, and optionally, a photoacid generator and/or an acid and/or a thermal acid generator. The invention further relates to a process for using such a composition.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of U.S. application Ser. No. 10/808,884, filed Mar.25, 2004, the contents of which are incorporated herein by reference inits entirety.

FIELD OF INVENTION

The present invention relates to novel positive-working, photoimageable,and aqueous developable antireflective coating compositions and theiruse in image processing by forming a thin layer of the novelantireflective coating composition between a reflective substrate and aphotoresist coating. Such compositions are particularly useful in thefabrication of semiconductor devices by photolithographic techniques,especially those requiring exposure with deep ultraviolet radiation.These coatings are particularly compatible for use with an edge beadremover.

BACKGROUND

Photoresist compositions are used in microlithography processes formaking miniaturized electronic components such as in the fabrication ofcomputer chips and integrated circuits. Generally, in these processes, athin coating of a film of a photoresist composition is first applied toa substrate material, such as silicon wafers used for making integratedcircuits. The coated substrate is then baked to evaporate any solvent inthe photoresist composition and to fix the coating onto the substrate.The baked and coated surface of the substrate is next subjected to animage-wise exposure to radiation.

This radiation exposure causes a chemical transformation in the exposedareas of the coated surface. Visible light, ultraviolet (UV) light,electron beam and X-ray radiant energy are radiation types commonly usedtoday in microlithographic processes. After this image-wise exposure,the coated substrate is treated with a developer solution to dissolveand remove either the radiation-exposed or the unexposed areas of thephotoresist.

There are two types of photoresist compositions, negative-working andpositive-working. When positive-working photoresist compositions areexposed image-wise to radiation, the areas of the photoresistcomposition exposed to the radiation become soluble in a developersolution while the unexposed areas of the photoresist coating remainrelatively insoluble to such a solution. Thus, treatment of an exposedpositive-working photoresist with a developer causes removal of theexposed areas of the photoresist coating and the formation of a positiveimage in the coating, thereby uncovering a desired portion of theunderlying substrate surface on which the photoresist composition wasdeposited. In a negative-working photoresist the developer removes theportions that are not exposed.

The trend towards the miniaturization of semiconductor devices has ledboth to the use of new photoresists that are sensitive to lower andlower wavelengths of radiation, and also to the use of sophisticatedmultilevel systems to overcome difficulties associated with suchminiaturization.

High resolution, chemically amplified, deep ultraviolet (100-300 nm)positive and negative tone photoresists are available for patterningimages with less than quarter micron geometries. There are two majordeep ultraviolet (uv) exposure technologies that have providedsignificant advancement in miniaturization, and these are lasers thatemit radiation at 248 nm and 193 nm. Examples of such photoresists aregiven in the following patents and incorporated herein by reference,U.S. Pat. No. 4,491,628, U.S. Pat. No. 5,350,660, EP 794458 and GB2320718. Photoresists for 248 nm have typically been based onsubstituted polyhydroxystyrene and its copolymers. On the other hand,photoresists for 193 nm exposure require non-aromatic polymers, sincearomatics are opaque at this wavelength. Generally, alicyclichydrocarbons are incorporated into the polymer to replace the etchresistance lost by eliminating the aromatic functionality. Furthermore,at lower wavelengths the reflection from the substrate becomesincreasingly detrimental to the lithographic performance of thephotoresist. Therefore, at these wavelengths antireflective coatingsbecome critical.

The use of highly absorbing antireflective coatings in photolithographyis a simpler approach to diminish the problems that result from backreflection of light from highly reflective substrates. The bottomantireflective coating is applied on the substrate and then a layer ofphotoresist is applied on top of the antireflective coating. Thephotoresist is exposed imagewise and developed. The antireflectivecoating in the exposed area is then typically etched and the photoresistpattern is thus transferred to the substrate. Most antireflectivecoatings known in the prior art are designed to be dry etched. The etchrate of the antireflective film needs to be relatively high incomparison to the photoresist so that the antireflective film is etchedwithout excessive loss of the resist film during the etch process. Thereare two known types of antireflective coatings, inorganic coatings andorganic coatings. However, both of these types of coatings have so farbeen designed for removal by dry etching.

In addition, photoresist patterns may be damaged or may not betransferred exactly to the substrate if the dry etch rate of theantireflective coating is similar to or less than the etch rate of thephotoresist coated on top of the antireflective coating. The etchingconditions for removing the organic coatings can also damage thesubstrate. Thus, there is a need for organic bottom antireflectivecoatings that do not need to be dry etched and can also provide goodlithographic performance, especially for compound semiconductor typesubstrates, which are sensitive to etch damage.

The novel approach of the present application is to use an absorbing,positive image-forming bottom antireflective coating that can bedeveloped by an aqueous alkaline solution, rather than be removed by dryetching, Aqueous removal of the bottom antireflective coating eliminatesthe dry etch rate requirement of the coating, reduces the cost intensivedry etching processing steps and also prevents damage to the substratecaused by dry etching. The absorbing bottom antireflective coatingcompositions of the present invention contain a crosslinking compoundand a polymer. The coating is cured and then upon exposure to light ofthe same wavelength as that used to expose the top positive photoresistbecome imageable in the same developer as that used to develop thephotoresist. This process greatly simplifies the lithographic process byeliminating a large number of processing steps. Since the antireflectivecoating is photosensitive, the extent of removal of the antireflectivecoating is defined by the latent optical image, which allows a gooddelineation of the remaining photoresist image in the antireflectivecoating.

Bilevel photoresists are known, as in U.S. Pat. No. 4,863,827, butrequire exposure of two different wavelengths for the top and bottomphotoresists, which complicates the processing of the lithography.

There are many patents that disclose antireflective coating compositionsbut these coatings are all cured to be insoluble in an aqueous developersolution and must be removed by dry etching. U.S. Pat. No. 5,939,236describes an antireflective coating containing a polymer, an acid orthermal acid generator, and a photoacid generator. However this film iscompletely crosslinked to make it insoluble in an alkaline aqueousdeveloper solution. The film is removed by a plasma gas etch. Examplesof other antireflective coating patents are U.S. Pat. No. 5,886,102,U.S. Pat. No. 6,080,530 and U.S. Pat. No. 6,251,562.

U.S. Pat. No. 4,910,122 discloses an aqueous developable antireflectivecoating, however the degree of solubility of the total film iscontrolled by the bake conditions. This antireflective coating is notphotoimageable, and therefore, there are no clearly defined soluble andinsoluble regions in the film. The dissolution of the antireflectivecoating is controlled by bake conditions and thus the antireflectivecoating is very sensitive to the developer normality and developingtime, and also gives poor resolution. High normality developer and/orlong develop times can cause excessive removal of the antireflectivecoating.

Another process for imaging photoresists using antirefective coatings isdisclosed in U.S. Pat. No. 5,635,333; however, the antireflectivecoating is not developed at the same time as the photoresist.

U.S. Pat. No. 5,882,996 describes a method of patterning dual damasceneinterconnections where a developer soluble antireflective coatinginterstitial layer is used. The antireflective coating is formed betweentwo photoresist layers and has a preferred thickness of 300-700angstroms, refractive index of 1.4-2.0 and is water soluble. Theantireflective coating is not photoimageable and there is no descriptionof the chemistry of the antireflective coating.

Acid sensitive antireflective coatings using differing chemistries aredisclosed in U.S. Pat. No. 6,110,653, U.S. Pat. No. 6,319,651, U.S. Pat.No. 6,054,254 and US 2004/0018451.

The novel antireflective composition of the present invention relates toa photoimageable, aqueous alkali developable, positive-workingantireflective coating. The antireflective coating composition of theinstant invention is coated on a substrate before applying a positivephotoresist layer, in order to prevent reflections in the photoresistfrom the substrate. The solid components of the antireflective coatingare soluble in common photoresist solvents and capable of forming acoating, and furthermore are compatible with edge-bead remover solvents.Edge-bead remover solvents are used to remove the build-up on the edgesof the antireflective coating formed during the spin coating process.This antireflective coating is photoimageable at the same wavelength ofactinic radiation as the top photoresist layer applied thereupon, and isalso developable with the same aqueous alkaline developing solution asthat used for typically developing a photoresist. The combination ofsingle exposure step and single development step greatly simplifies thelithographic process. Furthermore, an aqueous developable antireflectivecoating is especially desirable for imaging with photoresists that donot contain aromatic functionalities, such as those used for 193 nm and157 nm exposures. The novel composition enables a good image transferfrom the photoresist to the substrate, and also has good absorptioncharacteristics to prevent reflective notching and line width variationsor standing waves in the photoresist. Additionally, substantially nointermixing is present between the antireflective coating and thephotoresist film. The antireflective coatings also have good solutionstability and form thin films with good coating quality, the latterbeing particularly advantageous for lithography. When the antireflectivecoating is used with a photoresist in the imaging process, clean imagesare obtained, without damaging the substrate.

SUMMARY OF THE INVENTION

The present invention relates to a positive bottom photoimageableantireflective coating composition which is capable of being developedin an aqueous alkaline developer, wherein the antireflective coatingcomposition comprises a polymer comprising at least one recurring unitwith a chromophore group and one recurring unit with a hydroxyl and/or acarboxyl group, a vinyl ether terminated crosslinking agent, andoptionally, a photoacid generator. The invention may further comprise anacid or a thermal acid generator, preferably where the acid or the acidgenerated from the thermal acid generator has a pKa greater than 1.0.The invention further relates to a process for imaging using theantireflective composition of the present invention, especially with anedgebead removal step.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows examples of the structures of photoacid generators.

DESCRIPTION OF THE INVENTION

The present invention relates to a novel absorbing, photoimageable andaqueous developable positive image-forming antireflective coatingcomposition comprising a polymer comprising at least one unit with ahydroxyl and/or carboxyl group and at least one unit with an absorbingchromophore, a vinyl ether terminated crosslinking agent, andoptionally, a photoacid generator. Preferably the polymer isalkali-soluble and water insoluble. The invention further relates to aprocess for using such a composition, especially for irradiation fromabout 50 nm to about 450 nm.

The antireflective coating composition of the invention is coated on asubstrate and below a positive photoresist, in order to preventreflections in the photoresist from the substrate. This antireflectivecoating is photoimageable with the same wavelength of light as the topphotoresist, and is also developable with the same aqueous alkalinedeveloping solution as that used to typically develop the photoresist,thus forming a pattern in the antireflective coating. The antireflectivecoating composition comprises a polymer, a crosslinking agent and,optionally, a photoacid generator. The antireflective coatingcomposition is coated on a reflective substrate. The edge bead which mayform during the spinning process can then be removed using an edgebeadremoving solvent, since the polymer is still soluble in solvents used asedgebead removers. The coating is then baked to remove the solvent ofthe coating solution and also to crosslink the coating, in order toprevent, or minimize, the extent of intermixing between the layers andmake the coating insoluble in the aqueous alkaline developer. Althoughnot being bound by theory, it is believed that during the baking step areaction takes place between the crosslinking agent, especiallycompounds containing vinyl ether terminal groups, and the polymer withthe hydroxyl and/or a carboxyl group in the antireflective coating, toform acid labile groups within the coating. After baking and curing theantireflective coating is essentially insoluble in both an alkalinedeveloping solution and the solvent of the photoresist.

A positive photoresist is then coated on top of the cured antireflectivecoating and baked to remove the photoresist solvent. The coatingthickness of the photoresist is generally greater than the underlyingantireflective coating. Prior to exposure to actinic radiation both thephotoresist and the antireflective coating are insoluble in the aqueousalkaline developing solution of the photoresist. The bilevel system isthen imagewise exposed to radiation in one single step, where an acid isthen generated in both the top photoresist and the bottom antireflectivecoating. If a photoacid generator is present in the antireflectivecoating it is photolysed. When a photoacid generator is not present inthe antireflective coating, the acid may diffuse from the photoresistinto the antireflective coating. In a subsequent baking step, in theexposed regions the polymer of the antireflective coating with thecrosslinked sites (acid labile groups), are decrosslinked in thepresence of the photogenerated acid, thus making the polymer and hencethe antireflective coating soluble in the aqueous alkaline developer. Asubsequent developing step then dissolves the exposed regions of boththe positive photoresist and the antireflective coating, thus producinga positive image, and leaving the substrate clear for furtherprocessing.

The novel antireflective coating that is useful for the novel process ofthis invention comprises a crosslinking agent, a polymer, andoptionally, a photoacid generator. The polymer comprises at least oneunit with a hydroxyl and/or a carboxyl group and at least one unit withan absorbing chromophore. The absorbing chromophore is bound within thepolymer chain, as opposed to being a free dye in the composition, inorder to avoid decomposition or sublimation of the free dye during theprocess of baking the coating.

The polymer of the antireflective coating of the invention contains atleast one unit with hydroxyl and/or carboxyl group and at least one unitwith an absorbing chromophore. Examples of an absorbing chromophore arehydrocarbon aromatic moieties and heterocyclic aromatic moieties withfrom one to four separate or fused rings, where there are 3 to 10 atomsin each ring. Examples of monomers with absorbing chromophores that canbe polymerized with the monomers containing hydroxyl or carboxyl groupsare vinyl compounds containing substituted and unsubstituted phenyl,substituted and unsubstituted anthracyl, substituted and unsubstitutedphenanthryl, substituted and unsubstituted naphthyl, substituted andunsubstituted heterocyclic rings containing heteroatoms such as oxygen,nitrogen, sulfur, or combinations thereof, such as pyrrolidinyl,pyranyl, piperidinyl, acridinyl, quinolinyl. The substituents may be anyhydrocarbyl group and may further contain heteroatoms, such as, oxygen,nitrogen, sulfur or combinations thereof. Examples of such groups are(C₁-C₁₂) alkylene, esters, ethers, etc. Other chromophores are describedin U.S. Pat. No. 6,114,085, and in U.S. Pat. No. 5,652,297, U.S. Pat.No. 5,981,145, U.S. Pat. No. 6,187,506, U.S. Pat. No. 5,939,236, andU.S. Pat. No. 5,935,760, which may also be used, and are incorporatedherein by reference. The preferred chromophoric monomers are vinylcompounds of substituted and unsubstituted phenyl, substituted andunsubstituted anthracyl, and substituted and unsubstituted naphthyl; andmore preferred monomers are styrene, hydroxystyrene, acetoxystyrene,vinyl benzoate, vinyl 4-tert-butylbenzoate, ethylene glycol phenyl etheracrylate, phenoxypropyl acrylate, N-methyl maleimide,2-(4-benzoyl-3-hydroxyphenoxy)ethyl acrylate, 2-hydroxy-3-phenoxypropylacrylate, phenyl methacrylate, benzyl methacrylate, 9-anthracenylmethylmethacrylate, 9-vinylanthracene, 2-vinylnaphthalene, N-vinylphthalimide,N-(3-hydroxy)phenyl methacrylamide,N-(3-hydroxy-4-hydroxycarbonylphenylazo)phenyl methacrylamide,N-(3-hydroxyl-4-ethoxycarbonylphenylazo)phenyl methacrylamide,N-(2,4-dinitrophenylamino phenyl)maleimide,3-(4-acetoaminophenyl)azo-4-hydroxystyrene,3-(4-ethoxycarbonylphenyl)azo-acetoacetoxy ethyl methacrylate,3-(4-hydroxyphenyl)azo-acetoacetoxy ethyl methacrylate,tetrahydroammonium sulfate salt of 3-(4-sulfophenyl)azoacetoacetoxyethyl methacrylate and equivalent structures. It is within the scope ofthis invention that any chromophore that absorbs at the appropriateexposure wavelength may be used alone or in combination with otherchromophores.

The polymer of the novel invention comprises at least one unit with ahydroxyl and/or a carboxyl group to provide alkaline solubility, and acrosslinking site. One function of the polymer is to provide a goodcoating quality and another is to enable the antireflective coating tochange solubility during the imaging process. The hydroxyl or carboxylgroups in the polymer provide one of the components necessary for thesolubility change. Examples of monomers which provide such a unit uponpolymerization are without limitations, substituted or unsubstitutedvinyl monomers containing a hydroxyl and or carboxyl group, such asacrylic acid, methacrylic acid, vinyl alcohol, hydroxystyrenes, vinylmonomers containing 1,1′,2,2′,3,3′-hexafluoro-2-propanol although anymonomer that makes the polymer alkali soluble and preferably waterinsoluble, may be used. The polymer may contain a mixture of monomerunits containing hydroxyl and/or carboxyl groups. Vinyl monomerscontaining the 1,1,1,3,3,3-hexafluoro-2-propanol group are exemplifiedwith the compounds represented by structures (1) to (6) and theirsubstituted equivalents.

Thus a polymer may be synthesized by polymerizing monomers that containa hydroxyl or carboxyl group with monomers that contain an absorbingchromophore. Alternatively, the alkali soluble polymer may be reactedwith compounds that provide the hydroxyl or carboxyl group and compoundsthat provide the absorbing chromophore. In the final polymer the mole %of the unit or units containing the hydroxyl or carboxyl group can rangefrom 5 to 95, preferably 10 to 90, and more preferably 20 to 80 and themole % of the absorbing chromophore unit in the final polymer can rangefrom 5 to 95, preferably 10 to 90 more preferably 20 to 80. It is alsowithin the scope of this invention that the hydroxyl or carboxyl groupis attached to the absorbing chromophore or that the chromophore isattached to the hydroxyl or carboxyl group, that is, both groups arepresent in the same unit. As an example the chromophoric groupsdescribed previously may have pendant hydroxyl and/or carboxyl groups orthat the chromophoric groups and the hydroxyl group and/or carbonylgroup are attached to the same group.

Other than the unit containing the hydroxyl and/or carboxyl group andthe unit containing the absorbing chromophore, the polymer may containother monomeric units, such units may provide other desirableproperties. Examples of the third monomer are —CR₁R₂—CR₃R₄—, where R₁ toR₄ are independently H, (C₁-C₁₀) alkyl, (C₁-C₁₀) alkoxy, nitro, halide,cyano, alkylaryl, alkenyl, dicyanovinyl, SO₂CF₃, COOZ, SO₃Z, COZ, OZ,NZ₂, SZ, SO₂Z₇ NHCOZ, SO₂NZ₂, where Z is H, or (C₁-C₁₀) alkyl, hydroxy(C₁-C₁₀) alkyl, (C₁-C₁₀) alkylOCOCH₂COCH₃, or R₂ and R₄ combine to forma cyclic group such as anhydride, pyridine, or pyrollidone, or R₁ to R₃are independently H, (C₁-C₁₀) alkyl, (C₁-C₁₀) alkoxy and R₄ is ahydrophilic group. Examples of the hydrophilic group, are given here butare not limited to these: O(CH₂)₂OH, O(CH₂)₂O(CH₂)OH, (CH₂)_(n)OH (wheren=0-4), COO(C₁-C₄) alkyl, COOX and SO₃X (where X is H, ammonium, alkylammonium. Other monomers may be methyl meth acrylate, butylmethacrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate.Monomeric units containing acid labile groups may also be used, such ashydroxystyrene, vinyl alcohol, (meth)acrylic acid capped with acidlabile groups. Examples of acid labile groups, without limitation, aresecondary and tertiary alkyls (up to 20 carbon atoms) with at least onehydrogen, acetals and ketals, trimrethylsilyl, and β-trimethylsilylsubstituted alkyls. Representative examples of acid labile groups aretert-butyl, tert-pentyl, isobornyl, 1-alkylcyclohexyl,1-alkylcyclopentyl, cyclohexyl, 2-alkyl-2-adamantyl,2-alkyl-2-norbornyl. Other examples of acid labile groups aretetrahydrofuranyl, tetrahydropyranyl, substituted or unsubstitutedmethoxycarbonyl, β-trialkylsilylalkyl groups (e.g. CH₂—CH₂Si(CH₃)₃,CH(—CH₂Si(CH₃)₃)₂, CH₂—CH(Si(CH₃)₃)₂ and the like.

Novolak resins can also be used as suitable polymers for antireflectivecoatings. These resins are typically produced by conducting acondensation reaction between formaldehyde and one or moremulti-substituted phenols, in the presence of an acid catalyst, such asoxalic acid, maleic acid, or maleic anhydride. Typical monomers may beformaldehyde, cresols, resorcinols, xylenols, etc.

Examples of polymers are novolaks, polyhydroxystyrenes, and copolymersof hydroxystyrene, where the other comonomers are at least one ofstyrene, vinyl alcohol, acrylic acid, methacrylic acid, acrylic esters,methacrylic esters, etc.

The polymers of this invention may be synthesized using any known methodof polymerization, such as ring-opening metathesis, free-radicalpolymerization, condensation polymerization, using metal organiccatalysts, or anionic or cationic copolymerization techniques. Thepolymer may be synthesized using solution, emulsion, bulk, suspensionpolymerization, or the like. The polymers of this invention arepolymerized to give a polymer with a weight average molecular weightfrom about 1,000 to about 1,000,000, preferably from about 2,000 toabout 80,000, more preferably from about 6,000 to about 50,000. When theweight average molecular weight is below 1,000, then good film formingproperties are not obtained for the antireflective coating and when theweight average molecular weight is too high, then properties such assolubility, storage stability and the like may be compromised. Thepolydispersity (Mw/Mn) of the free-radical polymers, where Mw is theweight average molecular weight and Mn is the number average molecularweight, can range from 1.0 to 10.0, where the molecular weights of thepolymer may be determined by gel permeation chromatography.

The novel antireflective coating composition is coated and then cured onthe substrate by the application of heat. Heating induces a crosslinkingreaction between the carboxyl group or hydroxyl group on the polymer andthe crosslinking agent, and the acid labile crosslinkages are formed. Aparticular acid labile acetal crosslinkage can easily be facilitatedwhen the crosslinking agent is a vinyl ether terminated compound and thepolymer contains a carboxyl group or hydroxyl group. The resultingstructure is highly solvent-resistant and impervious to theinterdiffusion of photoresist components. Such curing processes are thesame as those of the normal thermosetting antireflective coatings.

The vinyl ether terminated crosslinking agents that are useful in theinstant invention can be represented by the general structure (7):

wherein R is selected from (C₁-C₃₀) linear, branched or cyclic alkyl,substituted or unsubstituted (C₆-C₄₀) aryl, or substituted orunsubstituted (C₇-C₄₀) alicyclic hydrocarbon; and n≧2. It is believedthat the terminal vinyl ether group reacts with the hydroxyl or carboxylgroup of the polymer to give an acid labile acetal linkage. Examples ofsuch vinyl ether terminated crosslinking agents include bis(4-vinyloxybutyl) adipate; bis(4-vinyloxy butyl) succinate; bis(4-vinyloxy butyl)isophathalate; bis(4-vinyloxymethyl cyclohexylmethyl) glutarate;tris(4-vinyloxy butyl) trimellitate; bis(4-vinyloxy methyl cyclohexylmethyl) terephthalate; bis(4-vinyloxy methyl cyclohexyl methyl)isophthalate; bis(4-vinyloxy butyl) (4-methyl-1,3-phenylene)biscarbamate; bis(4-vinyloxy butyl) (methylene di-4,1-phenylene)biscarbamate; and triethyleneglycol divinylether,1,4-cyclohexanedimentanol divinyl ether, various Vectomer® vinyl ethermonomers supplied by Aldrich Company, and polymers bearing pendantvinyloxy groups. Other vinyl ether terminated crosslinking agents aredescribed in T. Yamaoka, et al., Trends in Photochem. Photobio., 7:45(2001); S. Moon, et al., Chem. Mater., 6:1854 (1994); or H. Schacht, etal., ACS Symp. Ser. 706:78 (1998) which may also be used, and areincorporated herein by reference.

The vinyl ether terminated crosslinking agent is preferably added to theantireflective coating in a proportion which provides 0.20-2.00 molequivalents of vinyl ether crosslinking function per reactive group onthe polymer, especially preferred is 0.50-1.50 reactive equivalents perreactive group.

In one embodiment where the antireflective coating composition comprisesa photoacid generator, the photoacid generator in the antireflectivecoating and the photoacid generator in the photoresist, are sensitive tothe same wavelength of light, and thus the same radiant wavelength oflight can cause an acid to be formed in both layers. The acid in theexposed areas of the antireflective coating, present either throughdiffusion from the photoresist or through photogeneration from thephotoacid generator in the antireflective film, reacts with the acidlabile crosslinkages to decrosslink the polymer, thus making the exposedareas of the antireflective coating soluble in the aqueous alkalinedeveloper. The photoacid generator of the antirefletive coating chosendepends on the photoresist to be used. The photoacid generator (PAG) ofthe novel composition is selected from those which absorb at the desiredexposure wavelength, preferably 248 nm, 193 nm and 157 nm for deepultraviolet photoresists, and naphthoquinone diazides or sulfonium saltsfor 365 nm, 436 nm and broadband photoresists. Suitable examples of theacid generating photosensitive compounds include, without limitation,ionic photoacid generators (PAG), such as diazonium salts, iodoniumsalts, sulfonium salts, or non-ionic PAGs such as diazosulfonylcompounds, sulfonyloxy imides, and nitrobenzyl sulfonate esters,although any photosensitive compound that produces an acid uponirradiation may be used. The onium salts are usually used in a formsoluble in organic solvents, mostly as iodonium or sulfonium salts,examples of which are diphenyliodonium trifluoromethane sulfonate,diphenyliodonium nonafluorobutane sulfonate, triphenylsulfoniumtrifluoromethane sulfonate, triphenylsulfonium nonafluorobutanesulfonate and the like. Other compounds that form an acid uponirradiation that may be used, are triazines, oxazoles, oxadiazoles,thiazoles, substituted 2-pyrones. Phenolic sulfonic esters,bis-sulfonylmethanes, bis-sulfonylmethanes or bis-sulfonyldiazomethanes,triphenylsulfonium tris(trifluoromethylsulfonyl)methide,triphenylsulfonium bis(trifluoromethylsulfonyl)imide, diphenyliodoniumtris(trifluoromethylsulfonyl)methide, diphenyliodoniumbis(trifluoromethylsulfonyl)imide and their homologues are also possiblecandidates. Mixtures of photoactive compounds may also be used.

FIG. 1 shows examples of PAG structures, such as onium salts andhydroxyamic derivatives which are useful, where R₁, R₂ and R₃ areindependently alkyl, fluoroalkyl, F, OC_(n)H₂₊₁, OC_(n)F₂₊₁,CO₂-tert-Bu, OCH₂—CO₂— tert-Bu, OCH₂OCH₃ (n=1-4); X′ is anion ofnon-nucleophilic strong acid e.g. ⁻O(SO₂C_(n)F_(2n=1)), AsF₆ ⁻, SbF₆ ⁻,—N(SO₂C_(n)F_(2n=1))₂, ⁻C(SO₂C_(n)F_(2n=1))₃.

For exposure at 365 nm the photoacid generator can be sulfonium salts ordiazonaphthoquinones, especially 2,1,4-diazonaphthoquinones that arecapable of producing acids that can react with the acid labile groups ofthe polymer. Oxime sulfonates, substituted or unsubstitutednaphthalimidyl triflates or sulfonates are also known as photoacidgenerators. Any photoacid generator that absorbs light at the samewavelength as the top photoresist may be used. Photoacid generatorsknown in the art may be used, such as those disclosed in the U.S. Pat.No. 5,731,386, U.S. Pat. No. 5,880,169, U.S. Pat. No. 5,939,236, U.S.Pat. No. 5,354,643, U.S. Pat. No. 5,716,756, DE 3,930,086, DE 3,930,087,German Patent Application P 4,112,967.9, F. M. Houlihan et al., J.Photopolym. Sci. Techn., 3:259 (1990); T. Yamaoka et al., J. Photopolym.Sci. Techn., 3:275 (1990)), L. Schlegel et al., J. Photopolym. Sci.Techn., 3:281 (1990) or M. Shirai et al., J. Photopolym. Sci. Techn.,3:301 (1990), and incorporated herein by reference.

The solvent for the antireflective coating is chosen such that it candissolve all the solid components of the antireflective coating.Examples of suitable solvents for the antireflective coating compositionare cyclohexanone, cyclopentanone, anisole, 2-heptanone, ethyl lactate,propylene glycol monomethyl ether acetate, propylene glycol monomethylether, butyl acetate, gamma butyroacetate, ethyl cellosolve acetate,methyl cellosolve acetate, methyl 3-methoxypropionate, ethyl pyruvate,2-methoxybutyl acetate, diacetone alcohol, diethyl carbonate,2-methoxyethyl ether, but ethyl lactate, propylene glycol monomethylether acetate, propylene glycol monomethyl ether or mixtures thereof arepreferred. Solvents with a lower degree of toxicity and good coating andsolubility properties are generally preferred.

The composition of the present invention may further comprise an acid ora thermal acid generator. Crosslinking can take place between a polymercontaining a hydroxyl and/or carboxyl group and a crosslinking agent inthe presence of heat, however, typically reaction times may be long.Thermal acid generators or acids are used to accelerate the crosslinkingreaction and are desirable for instances where short curing times arepreferred. Thermal acid generators liberate the acid upon heating. Anyknown acids or thermal acid generators may be used, exemplified withoutlimitations, by 2,4,4,6-tetrabromocyclohexadienone, benzoin tosylate,squaric acid, 2-nitrobenzyl tosylate, chloroacetic acid, toluenesulfonicacid, methanesulfonic acid, nonaflate acid, triflic acid, other alkylesters of organic sulfonic acids, salts of these mentioned acids.However, it has been found that for certain components some acids andacids produced by thermal acid generators, which have high acidity, canlead to undercutting and can prevent the desired photoimaging processfrom taking place. Thus, it has been unexpectedly found that acids withmoderate acidity, i.e. with a pKa (−log₁₀ of the acid dissociationconstant) greater than 1.0 are preferred, especially in combination witha vinyl terminated crosslinking agent. Acids with a pKa of less than 5.0and greater than 1.0 are also preferred. The resulting acetal linkagesare easily cleavable in the presence of photogenerated acids. Examples,without limitations, of acids or acids derived from thermal acidgenerators with moderate acidity are maleic acid (pKa of 1.83),chloroacetic acid (pKa of 1.4), dichloroacetic acid (pKa of 1.48),oxalic acid (pKa of 1.3), cinnamic acid (pKa of 4.45), tartaric acid(pKa of 4.3), glycolic acid (pKa of 3.8), fumaric acid (pKa of 4.45),malonic acid (pKa of 2.8), cyanoacetic acid (pKa of 2.7), etc. Acidswhich are blocked by bases to form a thermal acid generator arepreferred. Acids, such as those described above, may be blocked withbases such as amines. Typical bases are triethyl amine, tripropyl amine,trimethyl amine, tributyl amine, tripentyl amine, tridodecyl amine etc.Additionally, diaryl or trialkyl sulfonium salts with anions of weakacids, such as carboxylic acid or aryl carboxylic acid may be used.Acids which are blocked by bases may be formed by combining the acidwith a base, where the acid:base ratio ranges from about 1:1 to about1:3. Further examples of acids with the desired pKa and their salts canbe found by one of ordinary skill in the art by reviewing the availableliterature, such as in CRC Handbook of Chemistry and Physics, publishedby CRC Press Inc. and incorporated herein by reference. In someembodiments it may also be desirable that the thermal acid be such thatonce the acid is generated it does not remain permanently in the coatingand therefore does not facilitate the reverse reaction, but is removedfrom the film. It is believed that, once crosslinking takes place theacid is decomposed or volatilized by heat and the decomposition productsare baked out of the film, or the acid may sublime from the coating.Thus none or very little of the free acid remains in the film aftercuring, and the reverse reaction causing the decomposition of the acetallinkage does not take place. Thermal acid generators which can generatean acid and then be removed prior to coating of the photoresist arepreferred in some cases. Weak acids that remain in the film may also befunctional, as they may not greatly hinder the decomposition of theacetal linkage. The acid or acid derived from the thermal acid generatoris preferably removed from the antireflective coating at temperaturesranging from about 130° C. to about 220° C., more preferably 150° C. toabout 200° C. The acids or thermal acid generators may be present in theantireflective composition at levels ranging from 0.1 to 25 weight % ofsolids, especially 0.1 to about 5 weight %.

Typical antireflective coating compositions of the present invention maycomprise up to about 15 percent by weight of the solids, preferably lessthan 8 percent, based on the total weight of the coating composition.The solids may comprise from 0 to 25 weight percent of the photoacidgenerator, 50 to 99 weight percent of polymer, 1 to 50 weight percent ofthe crosslinking agent and optionally 0 to 25 weight percent of the acidor thermal acid generator, based on the total solids content of theantireflective coating composition. Preferably the photoacid generatorlevel ranges from about 0.01 to about 20 weight %. Preferably thecrosslinking agent ranges from about 5 to about 40 weight percent, morepreferably 10 to 35 weight percent. The solid components are dissolvedin the solvent, or mixtures of solvents, and filtered to removeimpurities. The components of the antireflective coating may also betreated by techniques such as passing through an ion exchange column,filtratlon, and extraction process, to improve the quality of theproduct.

Other components may be added to the antireflective composition of thepresent application in order to enhance the performance of the coating,e.g. lower alcohols, dyes, surface leveling agents, adhesion promoters,antifoaming agents, etc. These additives may be present at up to 30weight percent level. Other polymers, such as, novolaks,polyhydroxystyrene, polymethylmethacrylate and polyarylates, may beadded to the composition, providing the performance is not negativelyimpacted. Preferably the amount of this polymer is kept below 50 weight% of the total solids of the composition, more preferably 35 weight %,and even more preferably below 20 weight %. Bases may also be added tothe composition to enhance stability. Both photobases and nonphotobasesare known additives. Examples of bases are amines, ammonium hydroxide,and photosensitive bases. Particularly preferred bases aretetrabutylammonium hydroxide, triethanolamine, diethanol amine,trioctylamine, n-octylamine, trimethylsulfonium hydroxide,triphenylsulfonium hydroxide, bis(t-butylphenyl)iodonium cyclamate andtris(tert-butylphenyl)sulfonium cyclamate.

The absorption parameter (k) of the novel composition ranges from about0.1 to about 1.0, preferably from about 0.15 to about 0.7 as measuredusing ellipsometry. The refractive index (n) of the antireflectivecoating is also optimized. The n and k values can be calculated using anellipsometer, such as the J. A. Woollam WVASE VU-302™ Ellipsometer. Theexact values of the optimum ranges for k and n are dependent on theexposure wavelength used and the type of application. Typically for 193nm the preferred range for k is 0.1 to 0.75, for 248 nm the preferredrange for k is 0.15 to 0.8, and for 365 nm the preferred range is from0.1 to 0.8. The thickness of the antireflective coating is less than thethickness of the top photoresist. Preferably the film thickness of theantireflective coating is less than the value of (wavelength ofexposure/refractive index), and more preferably it is less than thevalue of (wavelength of exposure/2 times refractive index), where therefractive index is that of the antireflective coating and can bemeasured with an ellipsometer. The optimum film thickness of theantireflective coating is determined by the exposure wavelength,refractive indices of the antireflective coating and of the photoresist,absorption characteristics of the top and bottom coatings, and opticalcharacteristics of the substrate. Since the bottom antireflectivecoating must be removed by exposure and development steps, the optimumfilm thickness is determined by avoiding the optical nodes where nolight absorption is present in the antireflective coating.

The antireflective coating composition is coated on the substrate usingtechniques well known to those skilled in the art, such as dipping, spincoating or spraying. Various substrates known in the art may be used,such as those that are planar, have topography or have holes. Examplesof semiconductor substrates are crystalline and polycrystalline silicon,silicon dioxide, silicon (oxy)nitride, aluminum, aluminum/siliconalloys, and tungsten. In certain cases there can be a buildup ofphotoresist film at the edges of the substrate, referred to as edgebead. This edge bead can be removed using a solvent or mixture ofsolvents using techniques well known to those of ordinary skill in theart. The composition of the present invention is particularly compatiblewith edge bead removers. Typical solvents used for edge bead removersare ethyl lactate, butyl acetate, propyleneglycolmonomethyletheracetate, propyleneglycol monomethylether, or mixturesthereof. The coating is then cured. The preferred range of temperatureis from about 120° C. to about 240° C. for about 30-120 seconds on a hotplate or equivalent heating unit, more preferably from about 150° C. toabout 200° C. for 45-90 seconds. The film thickness of theantireflective coating ranges from about 20 nm to about 300 nm. Theoptimum film thickness is determined, as is well known in the art, to bewhere good lithographic properties are obtained, especially where nostanding waves are observed in the photoresist. It has been unexpectedlyfound that for this novel composition very thin coatings can be used dueto the excellent absorption and refractive index properties of the film.The cured antireflective coating is also insoluble at this stage in thealkaline developing solution. The photoresist can then be coated on topof the antireflective coating.

Positive photoresists, which are developed with aqueous alkalinesolutions, are useful for the present invention, provided thephotoactive compounds in the photoresist and the antireflective coatingabsorb at the same exposure wavelength used for the imaging process forthe photoresist. Positive-working photoresist compositions are exposedimage-wise to radiation, those areas of the photoresist compositionexposed to the radiation become more soluble to the developer solution(e.g. a rearrangement reaction occurs) while those areas not exposedremain relatively insoluble to the developer solution. Thus, treatmentof an exposed positive-working photoresist with the developer causesremoval of the exposed areas of the coating and the formation of apositive image in the photoresist coating. Photoresist resolution isdefined as the smallest feature which the resist composition cantransfer from the photomask to the substrate with a high degree of imageedge acuity after exposure and development. In many manufacturingapplications today, resist resolution on the order of less than onemicron are necessary. In addition, it is almost always desirable thatthe developed photoresist wall profiles be near vertical relative to thesubstrate. Such demarcations between developed and undeveloped areas ofthe resist coating translate into accurate pattern transfer of the maskimage onto the substrate. This becomes even more critical as the drivetoward miniaturization reduces the critical dimensions on the devices.

Positive-acting photoresists comprising novolak resins andquinone-diazide compounds as photoactive compounds are well known in theart. Novolak resins are typically produced by condensing formaldehydeand one or more multi-substituted phenols, in the presence of an acidcatalyst, such as oxalic acid. Photoactive compounds are generallyobtained by reacting multihydroxyphenolic compounds with naphthoquinonediazide acids or their derivatives. The sensitivity of these types ofresists typically ranges from about 300 nm to 440 nm.

Photoresists sensitive to short wavelengths, between about 180 nm andabout 300 nm can also be used. These photoresists normally comprisepolyhydroxystyrene or substituted polyhydroxystyrene derivatives, aphotoactive compound, and optionally a solubility inhibitor. Thefollowing references exemplify the types of photoresists used and areincorporated herein by reference, U.S. Pat. No. 4,491,628, U.S. Pat. No.5,069,997 and U.S. Pat. No. 5,350,660. Particularly preferred for 193 nmand 157 nm exposure are photoresists comprising non-aromatic polymers, aphotoacid generator, optionally a solubility inhibitor, and solvent.Photoresists sensitive at 193 nm that are known in the prior art aredescribed in the following references and incorporated herein, EP794458, WO 97/33198 and U.S. Pat. No. 5,585,219, although anyphotoresist sensitive at 193 nm may be used on top of the antireflectivecomposition of this invention.

A film of photoresist is then coated on top of the cured antireflectivecoating and baked to substantially remove the photoresist solvent. Thephotoresist and the antireflective coating bilevel layers are thenimagewise exposed to actinic radiation. In a subsequent heating step theacid generated during exposure step reacts to de-crosslink the polymerof the antireflective coating composition and thus rendering the exposedregion of the antireflective coating alkali soluble in the developingsolution. The temperature for the postexposure bake step can range from40° C. to 200° C. for 30-200 seconds on a hot plate or equivalentheating system, preferably from 80° C. to 160° C. for 40-90 seconds. Insome instances, it is possible to avoid the postexposure bake, since forcertain chemistries, such as some acetal acid labile linkages,deprotection proceeds at room temperature. The polymer in the exposedregions of the antireflective coating is now soluble in an aqueousalkaline solution. The bilevel system is then developed in an aqueousalkaline developer to remove the photoresist and the antireflectivecoating. The developer is preferably an aqueous alkaline solutioncomprising, for example, tetramethyl ammonium hydroxide. The developermay further comprise additives, such as surfactants, polymers,isopropanol, ethanol, etc. The process of coating and imagingphotoresist coatings and antireflective coatings is well known to thoseskilled in the art and is optimized for the specific type of photoresistand antireflective coating combination used. The imaged bilevel systemcan then be processed further as required by the manufacturing processof integrated circuits, for example metal deposition and etching.

Each of the documents referred to above are incorporated herein byreference in its entirety, for all purposes. The following specificexamples will provide detailed illustrations of the methods of producingand utilizing compositions of the present invention. These examples arenot intended, however, to limit or restrict the scope of the inventionin any way and should not is be construed as providing conditions,parameters or values which must be utilized exclusively in order topractice the present invention.

EXAMPLES

The absorption parameter (k) and the refractive index (n) were measuredusing variable angle spectrophotometric ellipsometry. The bottomantireflective coating (B.A.R.C.) solutions were spin coated on primedsilicon wafers and baked to get a given film thickness. The coatedwafers were then measured using an ellipsometer manufactured by J.A.Woollam or Sopra Corporation. The obtained data were fitted to get the kand n values of the B.A.R.C. films.

Synthesis Example 1

To a 250 ml 4 neck flask, equipped with a condenser, a thermometer, anitrogen gas inlet and a mechanical stirrer, were added methacrylateester of 9-anthracene methanol (AMMA) (4.2 g), 4-acetoxystyrene (13.8g), azobisisobutylonitrile (AIBN) (0.8 g) and propyleneglycolmonomethylether (PGME) (50 g). A solution was obtained and degassed for15 minutes. Then the reaction mixture was heated to 70° C. and stirredat that temperature for 5 hours under flowing nitrogen. After thecompletion of the polymerization, the obtained solution was cooled downto the room temperature and tetramethylammonium hydroxide (26 wt % inwater) solution (7 g) was added. The reaction temperature was raised to40° C. and was kept for 3 hours before being raised to 60° C. Afterheating at 60° C. for 8 hours, the reaction mixture was cooled down toroom temperature and was acidified to pH 6 using acetic acid. Theresultant polymer was precipitated into 600 ml of methanol and theobtained solid was filtered, washed with methanol and deionized water,and then dried. The precipitated polymer was redissolved in 60 g of PGMEand precipitated again into 600 ml of methanol. The solid was filtered,washed and dried at 40° C. under vacuum. The obtained polymer(represented by the structure (I)) had a weight average molecular weight(Mw) of 12,800 and number average molecular weight (Mn) of 5,400 asmeasured on a gel permeation chromatography (GPC) using polystyrenestandards.

Synthesis Examples 2-5

Polymers with structures (II) to (V) were synthesized in the similarprocedure as Synthesis Example 1 except using the different types andamount of monomers in accordance with the monomer ratio given in thestructures.

Example 1

A copolymer represented by structure (I) from Synthesis Example 1 (2.5g), tris(4-vinyloxy butyl) trimellitate (0.25 g, Vectomer® 5015,available from Aldrich Co.), and triphenylsulfonium nonaflate (0.05 g)were dissolved in 68 g propyleneglycol monomethylether acetate (PGMEA)and 29 g of propyleneglycol monomethylether (PGME) to form anantireflective coating composition. The solution was filtered through a0.1 μm filter.

Example 2

A copolymer represented by structure (I) from Synthesis Example 1 (3 g),bis(4-vinyloxy butyl) adipate (0.4 g, Vectomer®4060, available fromAldrich Co.), and oxalic acid (0.01 g) were dissolved in 67.6 g PGMEAand 28.8 g PGME to form an antireflective coating composition. Thesolution was filtered through a 0.1 μm filter.

Example 3

A copolymer represented by structure (II) from Synthesis Example 2 (2.6g), tris(4-vinyloxy butyl) trimellitate (0.26 g, Vectomer®5015,available from Aldrich), and triphenylsulfonium nonaflate (0.05 g) weredissolved in 68 g PGMEA and 29 g PGME to form an antireflective coatingcomposition. The solution was filtered through a 0.1 μm filter.

Example 4

A copolymer represented by structure (I) from Synthesis Example 1 (3 g),triethyleneglycol divinylether (0.6 g, RAPI-CURE® DVE-3, available fromISP (Japan) Ltd.), and oxalic acid (0.01 g) were dissolved in 67.6 gPGMEA and 28.8 g POME by stirring to form an antireflective coatingcomposition. The solution was filtered through a 0.1 μm filter.

Example 5

A copolymer represented by structure (III) from Synthesis Example 3 (4g), tris(4-vinyloxy butyl) trimellitate (0.5 g, Vectomer®5015, availablefrom Aldrich), and oxalic acid (0.02 g) were dissolved in 70 g PGMEA and30 g PGME stirring to form an antireflective coating composition. Thesolution was filtered through a 0.1 μm filter.

Example 6

A copolymer represented by structure (IV) from Synthesis Example 4 (2g), tris(4-vinyloxy butyl) trimellitate (0.2 g, Vectomer®5015, availablefrom Aldrich Co.), and oxalic acid (0.01 g) were dissolved in 70 g PGMEAand 30 g PGME by stirring to form an antireflective coating composition.The solution was filtered through a 0.1 μm filter.

Example 7

A copolymer represented by structure (V) from Synthesis Example 5 (2 g),tris(4-vinyloxy butyl) trimellitate (0.2 g, Vectomer® 5015, availablefrom Aldrich Co.), and oxalic acid (0.01 g) were dissolved in 70 g PGMEAand 30 g PGME by stirring to form an antireflective coating composition.The solution was filtered through a 0.1 μm filter.

Example 8

The solution prepared in Example 1 was spin coated onto a 6 inch siliconwafer at 2500 rpm for 60 seconds and then baked on a hot plate at 170°C. for 90 seconds to form a cured antireflective coating layer. The filmthickness of the coating, as determined by ellipsometry manufactured byJ.A. Woollam company or by Sopra corporation, was about 700 Å. Byobserving the coated wafers, it was seen that the edge-bead formedduring the coating process on the antireflective coating could easily beremoved with a back-side rinse of a silicon wafer with a mixture of 30wt % PGMEA and 70 wt % PGME, an edgebead removing solvent.

The solutions prepared in Examples 1-8 were spin coated on 6 inchsilicon wafers and baked on a hot plate at different temperatures (eachbaking temperature 2 wafers for each sample). One coated wafer from eachof the set of B.A.R.C coatings was puddled with PGMEA, a commonphotoresist solvent, and the other with developer, each for 60 secondsand then spin dried. No obvious film thickness change in theantireflective layer was observed on the wafers when baked above 150°C., indicating that the films were highly crosslinked andsolvent-resistant, thus there would be no intermixing with thephotoresist solvent when the photoresist was coated over the B.A.R.C.When a comparative test was performed on the formulations preparedwithout the vinyl ether terminated crosslinking agent, it was observedthat the entire coating could be removed both in PGMEA and thedeveloper.

Example 9

The solutions prepared in Examples 1-4 were spin coated on 6 inchsilicon wafers baked at 170° C. for 90 seconds to give a thickness of 60nanometers. Then a DUV photoresist, AZ® DX6270P (available from Clariant(Japan) K. K.) was coated thereon and softbaked at 120° C. for 90seconds to give a thickness of 0.45 micron. The coated wafers wereimagewise exposed using Cannon FPA-3000 EX5 248 nm stepper. The exposedwafers were postexposure baked for 90 seconds at 130° C., followed by apuddle development of 60 seconds with AZ® 300 MIF Developer (2.38 weight% tetramethyl ammonium hydroxide aqueous solution available fromClariant Corp.). The secondary electron microscope results showed at 22mJ/cm², both the 0.20 μm 1:1 dense lines and 0.20 μm isolated lines wascompletely opened both in the photoresist layer and the antireflectivecoating layer. No obvious standing waves due to the reflection from thesubstrate were observed on the pattern profiles.

Example 10

1.5 g of poly(hydroxystyrene-methacrylate) (55/45 molar ratio), 0.075 gof oxalic acid/triethylamine (1:1), 0.06 g of triphenylsulfoniumtriflate, and 0.225 g of Vectomer™ 5015 (available from Aldrich Corp.)were dissolved in 98.5 g of ethyl lactate to give the B.A.R.C. solution.The solution was filtered through 0.2 μm microfilter. The B.A.R.C.coating gave a refractive index (n) and absorption (k) at 193 nm of 1.59and 0.62 respectively as measured by a J. A. Woollam WVASE VU-302™Ellipsometer.

The B.A.R.C. solution was coated on a primed silicon wafer heated on ahotplate at 200° C. for 60 seconds to give a film thickness of 35 nm.The B.A.R.C. wafer was coated with AZ®1020P photoresist (available fromClariant Corp., Somerville, N.J.) with a film thickness of 330 nm. Thewafer was then baked on a hotplate for 120° C. for 60 seconds. Thecoated wafer was exposed using an ISI 193 nm ministepper for imagewiseexposure. The exposed wafer as then post exposure baked for 90 secondsat 130° C. and followed with a 30-second puddle development at 23° C.using of AZ® 300 MIF Developer. Using a secondary electron microscope,0.15 μm photoresist/B.A.R.C. lines (1:1) were obtained at a dose of 40mJ/cm².

Example 11

0.075 g of poly(hydroxystyrene-methacrylate) (55/45 molar ratio), 0.015g of cyanoacetic acid, and 0.022 g of Vectomer™5015 were dissolved in8.0 g of propylene glycol monomethyl ether. The solution was filteredthrough 0.2 μm microfilter.

The B.A.R.C. solution was coated on a primed silicon wafer and heated ona hotplate at 175° C. for 60 seconds to give a film thickness of 293 Å.The B.A.R.C. wafer was coated with AZ® T430 photoresist (available fromClariant Corp., Somerville, N.J.), heated on a hotplate for 120° C. for60 seconds to give a film thickness of 116 nm. The coated wafer wasexposed using an ISI 193 nm ministepper for imagewise exposure. Theexposed wafer was then post exposure baked for 20 seconds at 120° C. andfollowed with a 30-second puddle development at 23° C. using of AZ® 300MIF Developer. Using a secondary electron microscope, 0.20 μmphotoresist B.A.R.C. lines (1:1) were obtained at a dose of 20 mJ/cm².

Example 12

The B.A.R.C. solution from Example 10 was coated on a primed siliconwafer and baked at 175° C. for 90 seconds to give a film thickness of499 Å. The B.A.R.C. wafer was coated with AZ® T430 photoresist(available from Clariant Corp., Somerville, N.J.), heated on a hotplatefor 120° C. for 60 seconds to give a film thickness of 116 nm. Thecoated wafer was exposed using an ISI 193 nm ministepper for imagewiseexposure. The exposed wafer was then post exposure baked for 20 secondsat 120° C. and followed with a 30-second puddle development at 23° C.using of AZ® 300 MIF Developer. Using a secondary electron microscope,0.35 μm photoresist/B.A.R.C. lines (1:1) were obtained at a dose of 21mJ/cm2.

1. A positive bottom photoimageable antireflective coating compositionwhich is capable of being developed in an aqueous alkaline developer,wherein the antireflective coating composition comprises a polymercomprising at least one recurring unit with a chromophore group and onerecurring unit with a hydroxyl and/or a carboxyl group, a vinyl etherterminated crosslinking agent, a thermal acid generator and optionally,a photoacid generator.
 2. The composition according to claim 1, whereinthe chromophore group is chemically bonded to the polymer and isselected from a compound containing aromatic hydrocarbon rings, asubstituted or unsubstituted phenyl group, a substituted orunsubstituted anthracyl group, a substituted or unsubstitutedphenanthryl group, a substituted or unsubstituted naphthyl group, asubstituted or an unsubstituted heterocyclic aromatic rings containingheteroatoms selected from oxygen, nitrogen, sulfur, and a mixturethereof.
 3. The composition according to claim 1, wherein the recurringunit containing a hydroxyl and/or a carboxyl group is derived from amonomer selected from acrylic acid, methacrylic acid, vinyl alcohol,hydroxystyrenes, copolymers of hydroxystyrene and vinyl monomerscontaining 1,1,1,3,3,3-hexafluoro-2-propanol.
 4. The compositionaccording to claim 1, wherein the chromophore group and the hydroxyland/or a carboxyl group are present in the same recurring unit.
 5. Thecomposition according to claim 1 comprising a vinyl ether terminatedcrosslinking agent represented by the general structure below;

wherein, R is selected from a (C₁-C₃₀) linear, branched or cyclic alkyl,substituted or unsubstituted (C₆-C₄₀) aryl, and substituted orunsubstituted (C₇-C₄₀) alicyclic hydrocarbon; and n≧2.
 6. Thecomposition of claim 1, further comprising an acid.
 7. The compositionof claim 1, where the acid derived from the thermal acid generator has apKa greater than 1.0.
 8. The composition of claim 1, where the acidderived from the thermal acid generator is selected from maleic acid,chloroacetic acid, dichloroacetic acid, oxalic acid, cinnamic acid,tartaric acid, glycolic acid, fumaric acid, malonic acid, cyanoaceticacid.
 9. The composition of claim 1, where the thermal acid generator isan acid blocked by a base, where the base is an amine and the acid isselected from maleic acid, chloroacetic acid, dichloroacetic acid,oxalic acid, cinnamic acid, tartaric acid, glycolic acid, fumaric acid,malonic acid, cyanoacetic acid.
 10. The composition of claim 1, wherethe base is selected from triethylamine, tripropyl amine, trimethylamine, tributyl amine, tripentyl amine and tridodecyl amine.
 11. Thecomposition of claim 1, where the acid derived from the thermal acidgenerator is diary or trialkyl sulfonium salts of anions of weak acids.12. The composition of claim 1, where the acid derived from the thermalacid generator has a pKa less than 5.0 and greater than 1.0.
 13. Thecomposition of claim 1, where the acid derived from the thermal acidgenerator is removed from the antireflective coating at temperaturesbelow 220° C.
 14. The composition according to claim 1 furthercomprising a dye.
 15. The composition according to claim 9, wherein thedye is selected from the group consisting of a monomeric dye, apolymeric dye and a mixture of a monomeric and a polymeric dye.
 16. Thecomposition according to claim 1i wherein the antireflective layer has ak value in the range of 0.1 to 1.0.
 17. The composition according toclaim 1, wherein the antireflective layer has a thickness less than thethickness of the photoresist.
 18. The composition according to claim 1,wherein the photoacid generator is sensitive to actinic radiation in therange of 50 nm to 450 nm.